1. Field of the Invention
The present invention generally relates to motorcycle exhaust systems. More particularly, the present invention relates to a motorcycle exhaust systems that comprise an exhaust pipe unit connected with an engine and a muffler unit connected with the exhaust pipe unit.
2. Description of the Related Art
In some motorcycles, a muffler is disposed below an engine of the motorcycle to lower the center of gravity of the vehicle as much as possible. Such a placement of the muffler lowers the center of gravity because the muffler typically is a heavy component. JP-A-2002-303133 discloses such a construction. In the Japanese reference, an engine is mounted between front and rear wheels. The exhaust gas from the engine is discharged through the exhaust pipe that extends from the engine. A silencer, or muffler, is attached to the end of the exhaust pipe. The silencer has a gas outlet that is positioned near the gas inlet. The silencer is mounted on a lower part of the engine such that the gas inlet faces the rear wheel and the exhaust pipe is connected to the gas inlet of the silencer because it extends toward the region of the rear wheel. In other words, the exhaust pipes of some cylinders extend to the region of a rear wheel to connect with the muffler from the rear while the exhaust pipes of the other cylinders extend above the muffler to connect with the first set of exhaust pipes.
In such an exhaust system, some of the exhaust pipes extend along a lateral side of the muffler such that the traverse dimension (e.g., the side-to-side measurement) of the motorcycle must be increased to accommodate both the exhaust pipes and the muffler. The increased transverse dimension at such a lowered location reduces the angle to which the motorcycle can be leaned during cornering.
In addition, some of the exhaust pipes extend through a region between a lower portion of the engine and an upper portion of the muffler. Thus, the engine needs to be mounted relatively high to accommodate the exhaust pipes. The muffler generally cannot be further lowered due to the desire for maintaining sufficient minimum road clearance. As a result of the engine being relatively raised, the center of gravity of the motorcycle is necessarily elevated.